1. Field of the Invention
The present invention relates to a roller unit in which a pressing force for nipping a sheet member or the like is adjustable, and a transport system of a sheet member in an image processing apparatus using the roller unit.
Moreover, the present invention relates to image reading apparatuses such as an image scanner for reading an original image, image forming apparatuses such as image processing apparatuses or the like in a copying machine or the like, and particularly, to a supply system of a sheet member in an image processing apparatus in which multi-transport of the sheet member can be prevented in a hopper sheet member supply method.
2. Description of Related Art
A roller is frequently used in various equipment fields and, for example, in a rolling line of a steel plate or a transport line of a flat-plate and large-sized material, equipment is usually constituted by arranging a large number of roller pairs on upper, lower and both sides of the line to guide or roll/mold the steel plate or the material. Not only in such large-sized equipment, but also in a field of so-called business machines for image formation or image reading, such as a copy machine, a facsimile apparatus, and an image scanner, various rollers are similarly utilized. For the roller of the business machine, an object to be nipped or guided is a sheet, and thus, a remarkably simplified and lightened structure is general in which, for example, resin is utilized.
The roller is used in various fields in this manner, and, when the steel plate is rolled or the sheet material is transported, and when the sheet is supplied or transported in the business machine, how to set a nipping force of the roller is very important. This nipping force is set in accordance with a distance between shafts of a pair of rollers or an elastic urging force which interacts between the rollers. Moreover, in the rolling equipment, the large-sized material transport equipment, and the like, the nipping force or a rolling force is adjusted by a hydraulic-pressure or pneumatic-pressure cylinder connected to the roller shaft, a link mechanism including a spring or the like. In the equipment including such cylinder and link mechanism, rigidity of a system for setting the nipping force or the rolling force is high, and occupied space therefor also increases.
On the other hand, even in the field associated with the business machine, a constitution for guiding paper and other sheet materials and transporting them due to a friction force by utilizing the pair of rollers, as described above, is employed. Even in such guiding or transporting by the pair of rollers, it is important to set the nipping force between the rollers. For example, in the image scanner, the nipping force before and after an image reading section is intensified to some degree so as to stabilize image reading. In simple guiding or transporting, the nipping force is preferably set to be slightly weak so as to prevent an excessively large tension from being applied to the sheet.
On the other hand, for the image scanner and other image reading or forming business machines, a very large number of components and circuits are incorporated in a limited space of a main body. Therefore, considering from the incorporated space, it is not practical to set the nipping force of the roller pair with the cylinder or link mechanism. This problem has been solved by incorporating the respective roller pair with higher position""s accuracy and appropriately determining the distance between the shafts in order to set the nipping force.
However, in a case in which the nipping force is adjusted only with the distance between the shafts of the roller pair, if the incorporating precision of the roller pair is not higher, a desired object cannot be achieved. That is to say, since there is existed a manufacturing error of the roller itself and an incorporating error to a support member for supporting the roller, it is very difficult to set the nipping force with high-accuracy. Moreover, the support member for supporting the roller is securely disposed along a sheet transport path. Thus, if a position of the support member is fixed, change of the roller pair nipping force or another adjustment cannot be performed at all. Therefore, if the nipping force becomes too strong or weak in accordance with a sheet thickness or a paper quality, a function of transporting or guiding the sheet is deteriorated.
As described above, for the guiding roller of the large-sized equipment, the cylinder or the link mechanism can be used to arbitrarily change the roller nipping force. However, in the apparatus associated with the small-sized business machine, the nipping force of the guiding or transporting roller cannot be changed or adjusted, and this causes a problem that the image reading or the image formation is remarkably influenced.
The image reading apparatus such as an image scanner is provided, for example, with a sheet supply apparatus for feeding a sheet set on a hopper into the line. The sheet supply apparatus picks up and feeds out piled sheets one by one from the top, and is, in most cases, provided with a multi-transport preventing system for preventing two or more sheets from being fed by friction of the superposed sheets. The sheet supply apparatus provided with such multi-transport preventing system is described, for example, in JP-A-04-286558.
FIG. 16 is a schematic view showing a typical example of the conventional sheet supply apparatus provided with the multi-transport preventing system, and this apparatus has a constitution substantially similar to the constitution described in the aforementioned publication.
In FIG. 16, a hopper 51 for mounting and setting various types of sheets P such as document paper to be read is disposed on a base end of a reading line, and a supply roller 52 for picking up and feeding out an uppermost sheet P is disposed above the hopper 51. The hopper 51 is urged toward the supply roller 52 by a spring 51a, and the sheet P is pressed onto the supply roller 52 so that only the uppermost sheet P is fed out by friction with a peripheral surface of the roller. Moreover, even when a piled thickness of the sheets P changes, a pressing force to the supply roller 52 is held to be substantially constant by the spring 51a. 
On a line of an exit side of the hopper 51, in order to feed the sheet P to an image reading position, for example, three pairs of transport rollers 53, 54, 55 are arranged so that the sheet P fed from the hopper 51 is nipped, drawn out and transported downstream. Moreover, between the hopper 51 and a first pair of transport rollers 53, a separation roller 56 and a retard roller 57 are disposed as a multi-transport preventing system of the sheet P.
Multi-transport prevention by the separation roller 56 and retard roller 57 is broadly known in fields of an image reading apparatus and copying machine, and the retard roller 57 is constituted by attaching a torque limiter 57b around a main shaft 57a which is rotated in a direction of an arrow shown in FIG. 16 by a driving motor (not shown). The main shaft 57a of the retard roller 57 is connected to the driving motor (not shown) commonly used for the separation roller 56, and is urged upward by a spring for setting the nipping force with the separation roller 56 in FIG. 16. Since such a torque limiter 57b is disposed, when one sheet P is fed from the supply roller 52, the retard roller 57 receives a rotation torque of the separation roller 56 to rotate in a transport direction of the sheet P. Moreover, when two or more sheets P are redundantly transported and nipped, the retard roller 57 keeps rotating in the arrow direction, and the redundantly transported lower sheet P is pushed back toward the hopper 51.
However, in the conventional retard roller 57, there is used a torque limiter 57b with a fixedly set torque value. That is to say, an operation torque of the torque limiter 57b cannot be changed in real time. On the other hand, in such a machine as an image scanner used for reading various types of sheets P, paper quality, thickness and friction coefficient of the sheet P changes variously in accordance with the sheet P. Therefore, when the operation torque of the torque limiter 57b is set to be constant, a multi-transport preventing function of the sheet P cannot sufficiently be fulfilled in cooperation with the separation roller 56. Particularly, when a large number of originals are read in the image scanner and an electronic file of the data thereof is performed, if multi-transport occurs and thus only one original is not read, the information to be stored becomes insufficient, and whereby, the sheet multi-transport raises a very important problem.
On the other hand, if a multi-transport detection sensor is disposed on the downstream side of the separation roller 56 and retard roller 57, when the multi-transport of the sheet P cannot be inhibited, multi-transport is detected, and thereby, it is possible to take operations of stopping the transport of the sheet P and returning the sheet back to the hopper 51 side. Furthermore, frequency of the multi-transport of the sheet P variously changes in accordance with the paper quality, thickness and friction coefficient of the sheet P, and the sheet is classified into a sheet which easily causes the multi-transport, and a sheet which does not easily cause the multi-transport. Therefore, when the sheet easily causing the multi-transport is supplied, by adjusting the torque of the torque limiter 57b and the nipping force by the separation roller 56 and retard roller 57, the multi-transport of the sheet P can effectively be prevented.
However, in the conventional structure, the set torque of the torque limiter 57b is fixed, and additionally the set torque and the nipping force between the separation roller 56 and the retard roller 57 cannot be adjusted in a correlative manner. Therefore, even when the frequency of the multi-transport of the sheet P is high, the structure has to be used as it is, it is necessary to stop reading for each of frequently occurring multi-transports of the sheet P, and an operation efficiency is largely deteriorated.
An object of the present invention is to provide a pressing force adjustable roller unit, and a transport system of a sheet member in an image processing apparatus provided with the roller unit.
Therefore, according to a first aspect of the present invention, there is provided a pressing force adjustable roller unit comprising: a roller; a holding shaft having a length projecting from an end surface of an axial direction of the roller and rotatably holding the roller; a torsion spring connected to the holding shaft in a direction that the holding shaft projecting from the end surface of the roller is pressed downward; and torsion torque change means for changing a torsion torque of the torsion spring.
With such a constitution, by changing the torsion torque of the torsion spring, the pressing force of the roller can be changed.
Moreover, a constitution in which the roller unit is disposed to form a nipping portion with a transport drive roller is applied to the image processing apparatus in which sheet members such as paper are transported, and in this case the pressing force suitable for transporting the sheet member can easily be set.
In the first aspect of the present invention, the roller unit may comprise a holder to which the holding shaft is rotatably attached and which is provided with a support shaft with a torsion spring winding portion attached to an outer periphery. The holder is provided with a long hole in which the holding shaft projecting from the end surface of the roller can move in a torsion direction of the torsion spring. Furthermore, the torque change means may be constituted of an engaging arm projecting from the torsion spring winding portion, and a plurality of stoppers formed on the holder, for engagingly stopping the engaging arm in a position for changing a wind-up degree of the winding portion. This has an effect that simply by changing a positional relation of the engaging arm to the stopper, the roller pressing force can be changed at the same number of steps as the number of stoppers.
Moreover, according to a second aspect of the present invention, there is provided a transport system of the sheet member in an image processing apparatus, in the image processing apparatus for performing image reading from sheet members such as paper or image formation on the sheet member based on input image information, in which the aforementioned roller unit is disposed in a transport path for transporting the sheet member, and a transport drive roller is disposed to form a nipping portion with a roller of the roller unit and is rotationally driven. The system has an effect that the applying of the pressing force suitable for transporting the sheet member to the sheet member can realize stable sheet member transport.
In the second aspect, the roller unit with a strengthened torsion torque of the torsion spring may be disposed immediately before and after an image reading section or an image forming section in the transport path, and with the roller unit, an effect of improving an image reading and forming precision can be obtained.
Moreover, an object of the present invention is to provide a sheet member supply system in which an optimum combination of a rotation torque of a retard roller, a nipping force between the retard roller and a separation roller and a hopper behavior can realize secure multi-transport prevention.
Thus, according to a third aspect of the present invention, there is provided a sheet member supply system comprising: a hopper on which sheet members such as paper are piled; a supply roller for picking up the sheet member and feeding out the sheet member to an image processing system; and a multi-transport preventing roller pair of a separation roller and a retard roller disposed on a downstream side of the supply roller and in an entrance to the image processing system, so that the hopper can vertically move with respect to the supply roller. This constitution further comprises multi-transport detection means, disposed on the immediate downstream side of the roller pair of the separation roller and the retard roller, for detecting multi-transport of the sheet member. This system is constituted so that, when the sheet member multi-transport is detected by the multi-transport detection means, the hopper is shifted in a downward direction apart from the supply roller, a nipping force between the separation roller and the retard roller is reduced and a rotation torque of the retard roller is increased.
With this constitution, even when the multi-transport of the sheet members such as paper cannot be prevented by the separation roller and retard roller, after the multi-transport detection, only an uppermost sheet member among multi-transported sheet members is transported to the image processing system, remaining sheet members can be returned to a hopper side by the retard roller, and secure multi-transport prevention can therefore be realized.
In the third aspect, the retard roller may be included in a retard motor driving system utilizing a DC motor whose output shaft rotation torque is variable in accordance with a current application amount. Thus, a simple constitution of controlling a power supply amount to a retard motor utilizing the DC motor can achieve an effect of changing the rotation torque of the retard roller and the supply of the sheet member and the prevention of multi-transport.
Moreover, an object of the present invention is to provide a sheet member supply system for adjusting a set torque of a retard roller and a nipping force between the retard roller and a separation roller to obtain an optimum multi-transport preventing condition in accordance with a sheet member or a multi-transport detection frequency so that secure multi-transport prevention can be performed.
Thus, according to a fourth aspect of the present invention, there is provided a sheet member supply system provided with a supply roller for picking up sheet members such as piled sheets and feeding out the sheet members to an image processing system, and a multi-transport preventing roller pair of a separation roller and a retard roller disposed on a downstream side of the supply roller and in an entrance to the image processing system. The supply system further comprises an automatic nipping force adjustment system for adjusting a nipping force between the separation roller and the retard roller, a set torque adjustment system for adjusting a critical set torque for rotating the retard roller in a forward rotation direction from a direction reverse to a supply direction of the sheet member, and a control system which can automatically adjust the nipping force by the automatic nipping force adjustment system and the set torque by the set torque adjustment system in accordance with material properties such as a sheet member friction coefficient.
With the constitution, since the nipping force between the separation roller and the retard roller and the set torque of the retard roller can automatically be set in accordance with the material properties such as the sheet member friction coefficient, it is possible to set optimum conditions for the transport of the sheet member, and the multi-transport of the sheet member is prevented. Moreover, when a control of reducing the nipping force to rotate/drive the retard roller in the sheet supply direction is included, a plurality of filed sheets can also be supplied, and diversification of sheet member types to be treated can be handled.
In the fourth aspect, the set torque adjustment system may use as a drive source a DC motor which is connected to the retard roller and whose output shaft rotation torque is variable in accordance with a current application amount. Thereby, with a simple constitution of controlling a power supply amount to a retard motor utilizing the DC motor, a function that the retard roller set torque is changed and the sheet member multi-transport can be prevented can be obtained.
Further, according to a fifth aspect of the present invention, there is provided a sheet member supply system comprising a supply roller for picking up sheet members such as piled sheets and feeding out the sheet members to an image processing system, a multi-transport preventing roller pair of a separation roller and a retard roller disposed on a downstream side of the supply roller and in an entrance to the image processing system, and multi-transport detection means disposed on an immediate downstream side of the roller pair, for detecting multi-transport of the sheet member. The supply system further comprises an automatic nipping force adjustment system for adjusting a nipping force between the separation roller and the retard roller, and a set torque adjustment system for adjusting a critical set torque for rotating the retard roller in a forward rotation direction from a direction reverse to a supply direction of the sheet member. With the constitution, it is controlled that the automatic nipping force adjustment system and set torque adjustment system adjust the nipping force and set torque to be suitable for sheet member properties in accordance with the number of multi-transports detected by the multi-transport detection means per sheet member unit number or unit time.
In this constitution, for example, it is assumed that several sets of sheet layers of different paper qualities are piled and supplied, multi-transport does not occur in the sheets of a certain paper quality, but, multi-transport frequently occurs when shifting to the sheet layer of another paper quality. At the time, since the nipping force and the retard roller set torque can be adjusted to be suitable for the paper quality in accordance with the detection of the number of multi-transports, the multi-transport can be prevented in a learning functional manner with respect to the sheet members such as sheets of various paper qualities.
In the fifth aspect, the set torque adjustment system may use as a drive source a DC motor which is connected to the retard roller and whose output shaft rotation number is variable in accordance with a current application amount. Thereby, with a simple constitution of controlling a power supply amount to a retard motor utilizing the DC motor, an effect is produced that the retard roller set torque is changed and the sheet member multi-transport can be prevented.